Boodle Hatfield, representing Mr Major, said in a statement last night that the court application would be made before Christmas and would ensure that appropriate trusts and powers were conferred to benefit the princes and Diana's charities.
It said the action would deal "with circumstances which could not have been foreseen". This is understood to refer to the extra value placed on anything bearing Diana's image, signature or name after her death. The executors of the estate would also welcome powers to enable them to control and police the memorabilia.
Trust expert and solicitor Mark Stephens explained: "The Princes are entitled to all the income from the exploitation of Diana's trademark but they are giving it to the memorial fund.
"So what is in effect happening is that John Major, as their guardian, is seeking the court's official approval to pass the trademark rights from the Princes on to the memorial fund. John Major needs to gets the court's sanction to approve the move because he is giving money away from minors."
It was also announced that the lawyers Mishcon de Reya, who act for the Diana, Princess of Wales Memorial Fund, would stand down from acting in general for the executors - her mother, Mrs Frances Shand-Kydd, and elder sister, Lady Sarah McCorquodale.
Meanwhile Earl Spencer is seeking planning permission to erect a 6ft high iron railing fence around the island grave of his sister Diana, Princess of Wales.
Plans have been submitted to Daventry District Council for the blue fence to be erected around the island and its surrounding lake - 15ft to 20ft from the water's edge - in the grounds of Althorp House, the Spencer family seat near Northampton.
- Ian Burrell
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